The present invention relates to an oxide powder obtained by coating, for a powder matrix, the surface of each powder particle of the matrix comprising one or both of a metal oxide and a semi-metal oxide, or of a composite oxide or a mixed oxide prepared from the above metal and semi-metal oxides, with a coat of a metal oxide or semi-metal oxide identical with or different from the above metal or semi-metal oxide, a method for manufacturing thereof, and a product based on the use thereof.
As a conventional method for manufacturing such an oxide powder, a method for manufacturing composite particles whereby a powder matrix undergoes surface reformation through moisturization by a metal alkoxide so that the surface of its powder particle may receive a coating layer is disclosed (Japanese Patent Laid-Open No. Hei 5-170425). This method for manufacturing composite particles consists of uniformly dispersing silica particles (powder matrix) into an aqueous solution of a metal salt, the metal being chosen from the group comprising hydrolytic metals such as copper, iron, zirconium, aluminum, chromium and yttrium; forming a coat made of a metal compound on the surface of a silica particle through hydrolytic reaction; and thereby obtaining an oxide powder, each powder particle of which has its surface reformed.
The oxide powder obtained by the above method is highly pure, ensures a high quality because its coating layer hardly detach, and may be used in a wide field of applications as a catalyst, catalyst carrier or absorbent.
On the other hand, a slurry for CMP (Chemical Mechanical Polishing) comprising an abrasive composed of mixed crystal particles of silica and alumina is disclosed (Japanese Patent Laid-Open No. Hei 12-265161). This slurry is composed of silica and alumina mixed at a ratio (silica/alumina) of 1/9 to 1/1, and has a pH of 4 to 9.
The slurry having such a composition as described above, i.e., being composed of mixed crystal particles of silica and alumina as an abrasive agent, ensures a stable polishing activity because of its pH being stabilized close to neutrality, and a highly selective affinity between the insulating membrane and the metal membrane.
Moreover, the powder matrix here concerned, when it is incorporated in a printing sheet for a printer for an electronic device or in a printing material used as an OHP film, receives a further coat, i.e., an ink-receiving layer on the surface of its powder particle to enhance the visibility and adsorption of printed ink. Fine silica powder particles and alumina powder particles are used as a material of such an ink-receiving layer (for example, see Japanese Patent Laid-Open Nos. 2000-6513 and 2000-141877).
However, the method for manufacturing composite particles as disclosed in the above Japanese Patent Laid-Open No. Hei 5-170425 requires drying and pulverizing steps, which may raise the production cost. Further, with the aforementioned conventional methods for manufacturing composite particles, silica particles, after drying, tend to aggregate by capillary actions, which will require an additional step for pulverization. Therefore, the number of steps required for the manufacture of those particles will increase.
The oxide powder manufactured by the above conventional methods is used as an additive to a toner for electronic photography. The oxide powder comprising silica each powder particle of which has its surface reformed is added to a toner to provide the toner with fluency. In some cases, titania powder having its surface reformed may be added in combination with the silica powder, to further enhance charge stability and environment stability of the toner. However, there is a problem in that it is difficult to effectively control each activity of these powders. In addition, each powder may tend to detach from the surface of toner particles as a result of mixture.
The CPM slurry as disclosed in the Japanese Patent Laid-Open No. Hei 12-265161 may be disturbed in the dispersion of its particles if its pH shifts from neutrality, and thus its abrasive activity will be impaired.
Further, if silica powder is used as an ink-receiving layer as described in the Japanese Patent Laid-Open Nos. 2000-6513 and 2000-141877, although it certainly confers transparency to the printing material, it only thinly permits the adsorption of ink. Therefore, with the printing material incorporating such a silica powder, ink may spread on the surface of the printing material to blur the print, or the photo-resistance of the material may be impaired. If alumina powder is used instead as a material of the ink-receiving layer, adsorption of ink to the printing material may be improved but the transparency of the material will be impaired. In addition, if silica powder or alumina powder is used, the resulting slurry that is to serve as a material of the ink-receiving layer will become so unstable that it will become impossible to obtain a highly concentrated slurry from them.
The object of this invention is to provide an oxide powder and a method for manufacturing thereof, which comprises taking a powder matrix consisting of an oxide; and uniformly and at a low cost forming a coating layer consisting of an oxide identical with or different from the above oxide, on the surface of the powder matrix, and wherein both of the powder matrix and the coating layer can develop their respective physical and chemical characteristics satisfactorily.
A further object of this invention is to provide an oxide powder, a method for manufacturing thereof, and a product utilizing thereof whereby the oxide powder or the product is provided with or improved in:
fluency, charge controllability, charge stability, electric conductivity, mechanical strength, tackiness, dispersibility, dispersion stability, transparency, anti-precipitation, anti-blocking, rheologic performance, ultra-violet ray absorption, catalytic activity, inhibition of photocatalytic activity, abrasion activity, heat insulation, heat resistance, anion adsorption, etc.
The invention according to claim 1 provides a method for manufacturing an oxide powder comprising the steps of:
keeping a powder matrix in a fluent state, said powder matrix consisting of a first oxide composed of one or both of a metal oxide and a semi-metal oxide, or a composite or mixed oxide from those oxides, and having an absorbed water amount of 0.1 to 50%, an averaged particle diameter of 0.005 to 0.5 xcexcm and a surface hydroxyl group number of 0.1 to 25 xcexcmol/m2;
contacting, one or both of a halide and an alkoxide including metal or semi-metal identical with or different from the metal or semi-metal constituting said first oxide, with said powder matrix kept in the fluent state, by means of an inert carrier gas, and then heating them at a temperature of from 25 to 800xc2x0 C., to thereby coat said powder matrix by a coating layer consisting of a second oxide; and
heating a reaction by-product consisting of one or both of a hydrogen halide or an alcohol generated by said contacting, at a temperature of from 200 to 1000xc2x0 C. within the inert carrier gas to thereby eliminate the reaction by-product.
The invention according to claim 2 provides a method for manufacturing an oxide powder comprising the steps of:
keeping a powder matrix in a fluent state, said powder matrix consisting of a first oxide having an absorbed water amount of 0.1 to 50%, an averaged particle diameter of 0.005 to 0.5 xcexcm and a surface hydroxyl group number of 0.1 to 25 xcexcmol/m2,
contacting, a halide including metal or semi-metal identical with or different from the metal or semi-metal constituting said first oxide, with said powder matrix kept in the fluent state, by means of an inert carrier gas, and then heating them at a temperature of from 25 to 800xc2x0 C., to thereby coat said powder matrix by a coating layer consisting of a second oxide; and
heating a reaction by-product consisting of a hydrogen halide generated by said contacting, at a temperature of from 200 to 1000xc2x0 C. within the atmosphere to thereby eliminate the reaction by-product.
The manufacturing methods as described in claim 1 or 2 can not only lower the cost required for the production of an oxide powder, but allows a coating layer to be uniformly formed on the surface of each particle of the powder matrix.
The powder matrix is preferably silica, alumina or titania, and the metal element included in said halide or said alkoxide is preferably one, or two or more of elements selected from the group consisting of transition elements of the 3A, 4A, 5A, 6A, 7A, 8, 1B and 2B families and typical elements of the 3B, 4B and 5B families in the periodic table.
The invention according to claim 5 provides a method for manufacturing an oxide powder as described in any one of claims 1, 3 and 4 wherein, as shown in FIG. 2, said keeping step comprises the step of keeping, said powder matrix consisting of said first oxide having the absorbed water amount of 0.1 to 50% and the surface hydroxyl group number of 0.1 to 25 xcexcmol/m2, in the fluent state, by supplying said powder matrix to a fluidized bed reaction apparatus 21, and by circulating atmospheric air from the below through a baffle plate 24;
wherein said contacting step comprises the steps of adopting the inert carrier gas as a fluidizing gas, and circulating one or both of the halide and the alkoxide together with the carrier gas through the powder matrix kept in the fluent state through the baffle plate 24 to thereby coat said powder matrix by the coating layer consisting of the second oxide; and
wherein said heating step comprises the step of circulating the carrier gas through the baffle plate 24, to thereby eliminate the reaction by-product and to thereby discharge said powder matrix coated by said coating layer, from the fluidized bed reaction apparatus 21.
The invention according to claim 6 provides a method for manufacturing an oxide powder as described in any one of claims 2 to 4 wherein, as shown in FIG. 2, said keeping step comprises the step of keeping, said powder matrix consisting of said first oxide having the absorbed water amount of 0.1 to 50% and the surface hydroxyl group number of 0.1 to 25 xcexcmol/m2, in the fluent state, by supplying said powder matrix to a fluidized bed reaction apparatus 21, and by circulating atmospheric air from the below through a baffle plate 24;
wherein said contacting step comprises the steps of adopting the inert carrier gas as a fluidizing gas, and circulating the halide together with the carrier gas through the powder matrix kept in the fluent state through the baffle plate 24 to thereby coat said powder matrix by the coating layer consisting of the second oxide; and
wherein said heating step comprises the step of circulating atmospheric air through the baffle plate 24, to thereby eliminate the reaction by-product and to thereby discharge said powder matrix coated by said coating layer, from the fluidized bed reaction apparatus 21.
The manufacturing method as described in claim 5 or 6 makes it possible to manufacture, in a continuous manner, an oxide powder wherein a coating layer is uniformly formed on the surface of a powder matrix, to thereby further reduce the cost required for the production of an oxide powder.
In the case of analyzing elements of a population including the oxide powder manufactured by the above methods as constituent ingredients of the population, a relative dispersion among elements is within xc2x160%; and no more than one agglomerate of powder particles exists in 1000 powder particles of the population, or, in other words, only primary particles exist in every 1000 powder particles of the population, and no secondary particle exists in the same population.
The invention according to claim 8 provides an oxide powder having an averaged particle diameter of 0.006 to 0.5 xcexcm, comprising:
a powder matrix consisting of a first oxide having an averaged particle diameter of 0.005 to 0.5 xcexcm and composed of one or both of a metal oxide and a semi-metal oxide, or of a composite or mixed oxide from those oxides, and
a coating layer coating the surface of said powder matrix, said coating layer consisting of a second oxide identical with or different from said first oxide,
wherein said second oxide of said coating layer is chemically bonded to the surface of said first oxide of said powder matrix, and the surface of said first oxide of said powder matrix is uniformly coated by the coating layer by 60% or more.
The invention according to claim 9 provides an oxide powder as described in claim 8
wherein said powder matrix has an absorbed water amount of 0.1 to 50%, and a surface hydroxyl group number of 0.1 to 25 xcexcmol/m2, and
wherein the coated amount by said coating layer is 0.1 to 10 times the surface hydroxyl group number.
The invention according to claim 10 provides an oxide powder as described in claim 8 or 9 wherein said powder matrix further comprises silica, alumina or titania, or is a composite oxide or a mixed oxide comprising at least silica, alumina or titania.
The invention according to claim 11 provides an oxide powder as described in any one of claims 8 to 10
wherein the metal element included in said second oxide of said coating layer is one or two or more of elements selected from the group consisting of transition elements of the 3A, 4A, 5A, 6A, 7A, 8, 1B and 2B families and typical elements of the 3B, 4B and 5B families in the periodic table.
The oxide powder as described in any one of claims 8 to 11 ensures the satisfactory development of the physical and chemical characteristics of the powder matrix and its coating layer. The physical and chemical characteristics may include those as described in (1) to (7).
(1) If the coating layer includes titania, and the oxide powder is used as an additive for a toner for electronic photography, the coating layer will provide the toner with fluency and charge stability at the same time.
(2) If the coating layer includes alumina, the coating layer will improve the abrasive activity of the oxide powder, and provide the oxide powder with a heat insulating activity and anion adsorbing activity.
(3) If the coating layer includes silica, the coating layer will provide the oxide powder with dispersion stability, and improve the fluency of the oxide powder.
(4) If the coating layer includes cerium oxide, the coating layer will improve the abrasive activity of the oxide powder. If this oxide powder is added to silicone rubber to be kneaded, it will provide the silicone rubber with heat resistance.
(5) If the coating layer includes iron oxide, the oxide powder will provide silicone rubber with heat resistance as in (4).
(6) If the coating layer includes stannic oxide and antimony oxide, the coating layer will provide the oxide powder with electric conductivity.
(7) If the powder matrix is titania, the coating layer will inhibit its photo-catalytic activity.
An oxide powder as described in any one of claims 8 to 11 is preferably provided with hydrophobidity, by surface reforming by one or both of a silane coupling agent and a silicone compound.
The silane coupling is preferably a coupling agent represented by the following formula (1):
X4xe2x88x92nSiRn . . . xe2x80x83xe2x80x83(1) 
wherein X is any one of a hydroxyl group, an alkoxy group and a halogen atom, R is an alkyl group having 1 to 18 carbons, and n is an integer from 0 to 3.
The silane coupling agent may be a coupling agent as represented by the following formula (2):
R3SiNHSiR3 . . . xe2x80x83xe2x80x83(2) 
wherein R is an alkyl group having 1 to 18 carbons.
The silicone compound is preferably represented by the following formula (3): 
wherein the substitutional group represented by Rxe2x80x2 is any one of a methyl group and an ethyl group; Rxe2x80x3 is any one of a methyl group, an ethyl group and a hydrogen atom, or is an alkyl group including, as a part thereof, any one of a vinyl group, a phenyl group and an amino group; X is any one of a hydroxyl group, an alkoxy group, a halogen atom and an alkyl group; and m is an integer from 1 to 500.
An oxide powder as described in claim 16 preferably comprises the first oxide constituting a powder matrix which is a composite oxide or a mixed oxide including silica, or including at least silica; and the second oxide constituting the coating layer including a metal element. In this case, the second oxide constituting the coating layer is more preferably alumina, titania, zirconia or ceria. These oxide powders are utilized as a material for abrasives, or for forming the ink-receiving layer of printing materials. Such an abrasive is preferably incorporated in slurries for chemical/mechanical abrasion. The chemical/mechanical abrasive slurry containing such an oxide powder is highly stable after dispersion. If this slurry is used to abrade a material to be abraded, it is possible to abrade it at a high speed and give it a mirror-polished surface. Or, if such an oxide powder is used as a material for forming the ink-receiving layer of a printing material, the adsorbed amount of an anion-source compound to the oxide powder is preferably 150% or more than the adsorbed amount of the anion-source compound to the powder matrix.
The invention according to claim 21 provides an ink-receiving layer forming material containing an oxide powder as described in claim 20. This ink-receiving layer forming material is a stable slurry, although it contains a high concentration of an oxide powder. The content of the oxide powder in the ink-receiving layer forming material is preferably 5 to 30 wt %.
The invention according to claim 22 provides an ink-jet oriented print material consisting of, such as, paper, film, etc, which is obtained by coating and drying a slurry of said ink-receiving layer forming material of claim 21.
The ink-jet oriented print material as described in claim 22, if characters or images are printed on this material using an ink-jet printer, will ensure improved ink adsorption, and the transparency and photo-resistance of the print material. Further, the ink coat will not develop cracks nor cause blurs.
The invention according to claim 23 provides a toner oriented additive comprising said oxide powder as described in any one of claims 12 to 15 wherein said first oxide of said powder matrix is silica, and the second oxide of said coating layer is titania.
The toner oriented additive as described in claim 23 will improve the fluency and charge controllability of the toner.
The invention according to claim 24 provides a ultraviolet ray absorbing material comprising an oxide powder as described in any one of claims 8 to 11 wherein said first oxide of said powder matrix is titania, and said second oxide of said coating layer is any one of silica, alumina and iron oxide.
The ultraviolet ray absorbing material as described in claim 24 will not only improve the ultraviolet ray absorption of the product, but keep its own photo-catalytic activity inhibited.
The invention according to claim 25 provides an electrically conductive powder comprising an oxcide powder as described in any one of claims 8 to 11 wherein said first oxide of said powder matrix is silica, and said second oxide of said coating layer is titania, or antimony-doped stannic oxide.
The electrically conductive powder as described in claim 25, if it is used as a material of an electro-conductive coat, will improve the electro-conductivity of the coat.